The invention relates to forming extruded, simulated cedar shakes. More particularly, the invention relates to continuously processing shakes that have tapered cross sections.
Wooden shakes, or shingles, are widely known as a type of roofing material used to protect homes from rain, snow, and heat and to provide aesthetic appeal. However, wooden shakes inevitably, over time, rot, split, crack, warp, absorb water, or thermally expand. As a result, wooden shakes need to be replaced frequently in order to continue to protect the home.
Plastic shakes generally have been used to overcome the disadvantages of wooden shakes. Plastic is typically more resistant to drying and cracking than wood and, hence, lasts longer and needs less maintenance than wood. Further, plastic shakes are normally cheaper to mass-produce than cedar shakes. U.S. Pat. Nos. 5,635,125, 5,295,339, and 4,193,898 disclose various plastic shakes that were improvements over wooden shakes.
At first, plastic shingles were manufactured because they did not need to be replaced as often as wooden shakes. More recently, plastic shakes have been manufactured to go beyond the advantages that wood could ever attain. For example, the ""898 patent discloses a plastic shake that is fire resistant, lightweight, and pliable in cold weather. The ""339 patent discloses a plastic shake that is durable and facilitates installation. The ""339 patent also discloses a shake that helps insulate the home.
Initially, plastic shakes were injected molded, a process where melted plastic would be poured into a mold and the shake would form when the plastic hardened. This process generally produced good quality shakes but was time consuming and expensive. The molds are expensive to manufacture and the process of heating and cooling the plastic under controlled conditions may require a lot of time and energy. Further, one mold typically can accommodate only one shake and, hence, the number of shakes made per unit time was limited to the number of molds available. These manufacturing expenses may have been passed onto customers and were possibly limiting factors in mass-producing plastic shakes via injection molding.
U.S. Pat. Nos. 4,290,248, 5,088,910, and 5,094,058 disclose a method of making plastic shakes in a continuous process. The process involves the plastic to be continuously extruded from a die. Upon exiting the die, the extrusion would typically be finished, or nearly finished, in two dimensions and would only require one additional cut to finish each shake. This process is advantageous because the shakes completed quickly and generally produces more shakes than injection molding.
Although this continuous process is a significant improvement in the process of making plastic shakes, this process also has limitations. For example, although plastic is continuously extruded, typically only one shake at a time can be cut off the extrusion. Meaning the number of shakes made may be limited to the same number of cuts one makes on the extrusion.
Tapered shakes are usually produced because this geometry most resembles the look and feel of traditional, wooden shakes. Further, tapered shakes are stronger than flat ones because the exposed portions of the shakes that are to withstand the elements of nature are the thicker ends of the tapered shakes. U.S. Pat. No. 4,850,844 discloses an apparatus for making tapered shakes. The ""844 patent discloses that tapered shakes are produced by cutting the shakes from a block of plastic.
The disadvantage of making tapered shakes as disclosed in the ""844 patent is that shakes are cut and formed one at a time and this is, on average, time consuming.
What is desired, therefore, is an improved process for continuously forming plastic tapered shakes where shakes of varying widths can be cut from the extrusion. What is also desired is an apparatus for continuously producing plastic tapered shakes where a tapered extrusion is then further slit into several tapered extrusions in order to increase the number of shakes produced. What is also desired is an apparatus for continuously producing plastic tapered shakes that allows several extrusions to be simultaneously and independently extruded, shaped, and cut.
Accordingly, it is the object of this invention to provide an improved method and apparatus for continuously forming plastic tapered shakes.
Another object is to provide a method and apparatus that simultaneously and continuously forms plastic extrusions with tapered cross sections.
Another object is to provide a method and apparatus for simultaneously cutting shakes of varying widths and quantities.
A further object is to provide a method and apparatus for storing data for cutting shakes of varying widths and quantities.
These and other objects of the invention are achieved by a method and apparatus for providing an improved process for continuously forming plastic tapered shakes where the apparatus comprises: an extruder, a slitter for slitting an extrusion in a generally longitudinal direction, and a cutter for cutting the extrusion in a generally transverse direction.